Hardbottom reef communities are found close to shore over limestone rock covered by a thin sandy layer. Hardbottom communities have low species diversity, dominated by gorgonians, algae, sponges, and a few stony coral species. Hardbottom habitats provide important cover and feeding areas for many fish and invertebrates.

Gorgoniancourtesy Florida Keys National Marine Sanctuary

Hardbottom communities are often divided into two types:

Nearshore restricted hardbottom communities are subject to limited water movement. This bottom community is dominated by algae including epilithic algae that attaches itself directly to the limestone bottom as well as drift algae.

Nearshore high-velocity hardbottom communities are exposed to strong currents. Gorgonians, easily recognized with their rod-like appearance and flexibility, and sponges dominate these communities.